Squamous Cell Carcinoma (SCC Horse)

• Slowly growing malignant skin neoplasms.
• Especially mucous membranes are affected.
• Development of eye cancer.
• Impairment or loss of the eye.

• Most common type of eye cancer in horses.
• This test identifies a gene mutation that increases the risk of developing a SCC. → Risk Test
• Due to this mutation in the DNA, the DDB2 protein, which is responsible for DNA repair in UV light damage, is not correctly formed.
• SCC is particularly common in Haflinger Horses due to the frequent occurrence of this mutation in the breed.
• It has also been described in Belgian draft horses and Pecherons, as well as Rocky Mountain Horses, Connemara ponies, Holsteiners and Belgian Warmbloods.

This test detects a missense mutation in the DDB2 gene (c.1013 C > T p.Thr338Met).

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Inheritance: autosomal recessive

→ The risk of developing SCC is increased if both copies of the gene (scc/scc) are affected by the mutation. Animals with only one copy (N/scc) are clinically normal carriers.

Genotyp

N/N = normal

The horse has no copies of the genetic variant causative for SCC and therefore cannot pass it on to its offspring.

N/scc = a carrier

The horse is clinically healthy. The genetic variant causative for CSS will be passed on to its offspring with a probability of 50%.

scc/scc = at risk

The horse has an increased risk of developing SCC. The mutation will be passed on to its offspring with a probability of 100%.

• Carriers may be bred to normal animals (N/scc x N/N) without any risk of producing at risk offspring. The offspring should also be tested before breeding to determine if they are carriers or normal.
• When breeding two carriers (N/scc x N/scc), there is a probability of 25% for each foal to inherit two copies of the mutation (scc/scc) and therefore having an increased risk of developing SCC. This should be taken into consideration when planning breedings.

Bellone, R.R., Liu, J., Petersen, J.L., Mack, M., Singer-Berk, M., Drögemüller, C., Malvick, J., Wallner, B., Brem, G., Penedo, M.C., Lassaline, M.: A missense mutation in damage-specific DNA binding protein 2 is a genetic risk factor for limbal squamous cell carcinoma in horses. Int J Cancer :, 2017. Pubmed reference: 28425625. DOI: 10.1002/ijc.30744.

Singer-Berk, M., Knickelbein, K.E., Vig, S., Liu, J., Bentley, E., Nunnery, C., Reilly, C., Dwyer, A., Drögemüller, C., Unger, L., Gerber, V., Lassaline, M., Bellone, R.R.: Genetic risk for squamous cell carcinoma of the nictitating membrane parallels that of the limbus in Haflinger horses. Anim Genet :, 2018. Pubmed reference: 29999543. DOI: 10.1111/age.12695.

Further information is available at Online Mendelian Inheritance in Animals.